Degree of Purity for 2X2 Density Matrix and Its Use in Quantum Information Theory

Rubens Viana Ramos, Rui Fragassi Souza

DOI: 10.14209/sbrt.2001.06600040

Evento: XIX Simpósio Brasileiro de Telecomunicações (SBrT2001)

Keywords:

Abstract

"There are many coincidences that relate the treatment of quantum states in a two-dimensional space and the classical polarisation treatment, due to some similarities that occur in coherence matrix and density matrix. We use these similarities to separate the density matrix in a mixture of a pure state and a maximally mixed state. This mixture is controlled by the degree of purity, that measures how much pure is a quantum state, such as usually done with the coherence matrix of a partially polarised beam. After that, we use this degree of purity in quantum information theory. We find out its relationship with the von Neumann entropy and its use in quantum Kolmogorov distance, fidelity and mutual information."

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